6.
a n=25×6÷5= 30
b n=12×4÷6=8
c n=24×28÷14=48
d n=40×9÷60=6
e n la patrat=48×3=144 => n=12
f n+1=30×4÷24=5
g 2n+1=7×15÷21=5=> 2n= 5-1=4 => n=4÷2=2
h 2×(3n-2)=5n=> 6n-4=5n => n= 4
i 15n=12×(n+1) => 15n=12n+12 => 15n-12n=12 => 3n=12 => n=4
